A technique called a Multimedia Broadcast and Multicast Service (hereinafter, MBMS) has recently been standardized for distributing multimedia contents such as motion pictures and music, under the Wideband-Code Division Multiple Access (W-CDMA) system.
The MBMS has enabled broadcasting service of the contents utilizing the Forward Access Channel (hereinafter, FACH), which has conventionally been serving as the common channel, to thereby save the radio resource in response to the increase in demand for the multimedia service.
The FACH refers to the downlink common channel transmitted by the base transceiver station, which is utilized for transmitting control information and user data.
Accordingly, for example in the case where the system related to the MBMS includes the base transceiver station and a base transceiver station controller, and a plurality of cells is present under control of the base transceiver station, the base transceiver station can allocate each of the cells with the FACH for distributing the contents and transmit the same contents to the respective FACH.
The FACH serving as the common channel in the MBMS will now be described as the related art, based on the foregoing case as the example.
The base transceiver station controller instructs a maximum transmit power value to the base transceiver station, with respect to each FACH of the cells under the control of the base transceiver station.
To control the transmit power of the FACH, the base transceiver station controller then notifies the base transceiver station of relative value information corresponding to the maximum transmit power value, which serves as the information for controlling the transmit power.
Upon receipt of the relative value information, the base transceiver station adds the power according to the relative value information received, to the transmit power of each FACH, to thereby modify the transmit power of the relevant FACH.
Regarding the MBMS, methods of controlling the transmit power, to be carried out by the base station controller, can be found in patent documents 1 to 3.
[Patent document 1] Japanese Laid-open patent publication No. 2003-209881
[Patent document 2] Japanese Laid-open patent publication No. 2004-215305
[Patent document 3] Japanese Laid-open patent publication No. 2006-254179